Investors took fright today following reports that EDF, the French state electricity giant, would have to reimburse customers in France a total of €8.8 billion (£7.1 billion).

Although the group denied the claim that every French household would receive a cheque of up to €250 as a result of a billing blunder, its share price fell to a record low of €13.79 in morning trading in Paris.

Panic set in after the State Council, France’s highest administrative court, ruled illegal the tariffs set by ERDF, EDF’s grid operating unit, for the period 2009 to 2013.